Cementum

cementum in health and disease

1. CEMENTUM DR. BENITA MARIA REGI 1 st YEAR PG DEPT. OF PERIODONTOLOGY

2. CONTENTS INTRODUCTION DEFINITION HISTORY PHYSICAL CHARACTERISTICS STAGES IN CEMENTUM DEVELOPMENT CEMENTOGENESIS BIOCHEMICAL COMPOSITION CELLS OF CEMENTUM -CEMENTOCYTES - CEMENTOCLASTS CEMENTOIDS ARRANGEMENT OF FIBRILS

3. CLASSIFICATION FUNCTIONS CEJ CDJ INCREMENTAL LINES CEMENTUM RESORPTION AND REPAIR EXPOSURE OF CEMENTUM TO ORAL ENVIRONMENT AGE CHANGES IN CEMENTUM ABNORMALITIES OF CEMENTUM INFLUENCE OF SYSTEMIC DISESASES ON CEMENTUM NEOPLASMS ASSOCIATED WITH CEMENTUM APPLIED ASPECTS CONCLUSION REFERENCES

4. Cementum is a mineralized connective tissue that covers the roots of the teeth. Derived from Latin “ caementum ”, quarry stone. Component of tooth as well as periodontium. Provides anchorage for collagen fibre bundles of periodontal ligament. Therefore, root surface area covered by it represents the ground available for connective tissue attachment. INTRODUCTION

5. DEFINITION Cementum is the calcified, avascular mesenchymal tissue that forms the outer covering of the anatomic root . (Carranza) Cementum is a mineralized connective tissue, in part not unlike bone, that covers the entire surface of anatomical roots of teeth . ( Schroeder) Cementum is a hard, avascular connective tissue that covers the root of the teeth . ( TenCate’s )

6. It begins at the cervical portion of the tooth at the cemento -enamel junction and continues to the apex. Cementum furnishes a medium for the attachment of collagen fibers that bind the tooth to surrounding structures

7. HISTORY Though cementum of the root is critical for periodontal structure and tooth attachment and function, this tissue was not discovered and characterized on human teeth until a full century later than enamel and dentin. Advances in microscopy and histological procedures yielded the first detailed descriptions of human cementum in 1835 by Jan Purkinje and Anders Retzius , who identified acellular and cellular types of cementum, and the resident cementocytes embedded in the latter.

8. Comparative anatomy studies by Richard Owen and others over the latter half of 19 th century identified coronal and radicular cementum varieties across the Reptilian and Mammalia. The functional importance of cementum was not appreciated until detailed anatomical studies of the periodontium were performed by G.V. Black and others in the late 19 th and early 20 th centuries.

9. PHYSICAL CHARACTERSTICS HARDNESS: Less than dentin COLOUR : Light yellow (Enamel : by lack of luster and darker hue) PERMEABILITY: - Very permeable and permit the diffusion of dyes - Canaliculi of cellular cementum is contiguous with dentinal tubules in some areas - Decreases with age

10. THICKNESS: Cemental deposition continues throughout life. Deposition most rapid in apical areas, where it compensates for tooth eruption, which itself compensates for attrition. Varies form 16-60 micrometer on the coronal half to 150-200 micrometer in the apical third and furcation. Thicker on distal than on mesial surfaces Between 11 to 70 years of age thickness increases 3 times

11. PRE-FUNCTIONAL DEVELOPMENTAL STAGE The prefunctional portion of cementum is formed during root development. Since the formation of human tooth roots occurs over an extended period of time ranging between 3.75 and 7.75 years for permanent teeth, the prefunctional development of cementum is an extremely long-lasting process. During this period of time, the primary distribution of the main cementum varieties is determined for each root.

12. FUNCTIONAL DEVELOPMENTAL STAGE It commences when the tooth is about to reach the occlusal level, is associated with the attachment of the root to the surrounding bone and continues throughout life. It is mainly during the functional development that adaptive and reparative processes are carried out by the biological responsiveness of cementum, which in turn, influences the alterations in the distribution and appearance of the cementum varieties on the root surface with time .

13. CEMENTOGENESIS

14. BIOCHEMICAL COMPOSITION INORGANIC PORTION (45-50%) Mainly Calcium and Phosphate in the form of Hydroxyapatite Highest Fluoride content ORGANIC PORTION (50-55%) Collagenous Non-Collagenous

15. Mineral component of cementum is similar as in other calcified tissues i.e. hydroxyapetite{Ca10(PO4)6(OH)2} with small amount of calcium and phosphate also present. Hydroxyapetite content in cementum (45-50%) is lesser than that in bone (65%), enamel (97%) or dentin(70%). Hydroxyapetite crystals in cementum are average 55 nm wide and 8 nm thick and is smaller than crystals in enamel. INORGANIC CONTENT

16. COLLAGENOUS PORTION TYPE I (90%) : -Predominant TYPE III (5%) : - less cross linked. -high concentrations during development, repair. ORGANIC CONTENT

17. TYPE XII : - A fibril associated collagen with triple helix that binds with type I and non-collagenous proteins - Related to forces of occlusion. OTHERS : -Type V, VI

18. PROTEOGLYCANS : Heparan sulfate, Chondroitin sulfate , Keratan sulfate. *Cell-cell, cell-matrix interactions UNIQUE TO CEMENTUM: Cementum derived attachment protein. Cementum derived growth factor OSTEOPONTIN: Regulates mineralization OTHERS: Bone sialoprotein, Alkaline phosphatase, Osteonectin , Dentin sialoprotein NON- COLLAGENOUS PROTEINS

19. CELLS OF THE CEMENTUM

20. CEMENTOCYTES Cementoblasts incorporated into the cemental matrix. Lie in spaces known as lacunae. numerous cell processes or canaliculi, anastomose with similar processes of the adjacent cementocytes . Directed towards PDL & derive nutrition from PDL

21. CEMENTOCLASTS : Multinucleated cells Involved with cemental resorption

22. CEMENTOIDS Unmineralized layer of cementum on cemental surface ( precementum ) New layer forms as old calcifies 3 to 5 micrometer Lined by cementoblasts Connective tissue fibers from PDL pass between the cementoblasts Embedded portion- Sharpeys fibers

23. ARRANGEMENT OF FIBRILS The arrangement of collagen fibers in cementum can be grouped into two: Extrinsic fiber system Consists of principal fibers ( sharpeys fibers ) Mostly arranged at right angles to cementum. Intrinsic fiber system The fibers are dense and irregularly arranged within the cemental matrix.

24. extrinsic FIBERS( sharpey’s )

25. INTRINSIC FIBERS

26. Cementum can be classified based on following criteria Based on location on teeth Coronal cementum Radicular cementum Based on cellularity Acellular cementum (primary) Cellular cementum (secondary) CLASSIFICATION

27. Based on presence or absence of collagen fibrils in organic matrix Fibrillar cementum Afibrillar cementum On the basis of location, structure, function, rate of formation, biochemical composition and degree of mineralization cementum can be classified as:- Acellular Afibrillar Cementum. (AAC ) Acellular Extrinsic Fiber Cementum. (AEFC) Cellular Mixed Stratified Cementum. (CMSC) Cellular Intrinsic Fiber Cementum. (CIFC) Intermediate cementum.

28. TYPES OF CEMENTUM RADICULAR CEMENTUM Derivative of dental follicle, covers the entire dentin of the root from CEJ to the apex It extends partially into apical foramen to line the apical walls of the root canal CORONAL CEMENTUM In humans it is restricted to areas of reduced enamel epithelium

29. ACELLULAR CEMENTUM First formed cementum Covers cervial third or half of the root Contains sharpey’s fibers and intrinsic fibers but no cells Formed before tooth reaches occlusal plane Thickness-30-230micrometers

30. CELLULAR CEMENTUM Formed after tooth reaches occlusal plane More irregular Contains cementocytes in lacunae communicating with each other through anastomosing canaliculi Sharpey’s fibers occupy smaller portion. Intrinsic fibers are more in proportion.

31. Acellular cementum showing incremental lines running Parallel to long axis of tooth. Cellular cementum Showing cementocytes within lacunae.

32. Acellular Afibrillar Cementum It is a mineralized ground substance, containing no cells and is devoid of extrinsic and intrinsic collagen fibres . It is a product of cementoblasts. Found as coronal cementum at dentinoenamel junction. Thickness of 1-15micrometers.

33. Acellular afibrillar cementum is deposited as isolated patches over minor areas of enamel and dentin. Cementum islands represent isolated patches of acellular afibrillar cementum deposited on the enamel over small areas of the crown just coronal to the cementoenamel junction. Cementum spurs are found around the cementoenamel junction, where they cover minor areas of the enamel and the adjacent dentin of the root.

34. ACELLULAR-EXTRINSIC FIBRE CEMENTUM Extends from cervical margin to apical one third It is a product of fibroblasts and cementoblasts. Sharpey’s fibres are seen perpendicular to surface of cementum Composed almost entirely of densely packed collagen fibers and lacks cells. Approximately 30,000 fibres / mm 2 insert in it indicates its significant function in tooth anchorage to surrounding bone.

35. Since this type of cementum is formed slowly and regularly incremental lines are placed parallel to the surface and closer together than in cellular cementum. Main function of this cementum is anchorage. Thickness ranges between 30-230 µm

36. A thin layer of AEFC with densely packed extrinsic fibers cover the peripheral dentin. Cementoblasts and fibroblasts can be seen adjacent to cementum Arrangement of Collagen bundles in AEFC

37. CELLULAR INTRINSIC FIBRE CEMENTUM Contains cells, but no extrinsic collagen fibers. Formed on the root surface. Secreted by cementoblasts, fills the resorption lacunae. Mainly involved in adaptation and repair of cementum. Less mineralized

38. Although it has no important function in tooth attachment, it has important function as adaptation tissue that brings and maintains tooth in its proper position. CIFC has capacity to repair a resorption lacunae in a reasonable amount of time due to its capacity to grow much faster than any other cementum type

39. CELLULAR MIXED STRATIFIED CEMENTUM Extrinsic and intrinsic fibres and cells, forms the bulk of secondary cementum Co- product of fibroblasts and cementoblasts Apical third of roots and furcations Thickness varies from 100-1000 micrometer Also involved in adaptation and repair of cementum.

40. Structure of CMSC which in contrast to AEFC, contains cells and intrinsic fibers Cementocytes [black cells] reside in lacunae in CMSC or CIFC

41. INTERMEDIATE CEMENTUM Poorly defined zone near CDJ separating cementum from dentin, which doesnot exhibit characteristic feature of either dentin or cementum. It appears hyaline( structureless )and so its also called hyaline layer This layer represents area where HERS cells become trapped in a rapidly deposited dentin or cementum matrix giving rise to intermediate layer Usually occurs in the apical half of roots of molars and premolars.

42. Sometimes it’s a continuous layer or it may be also found only in isolated areas. The probable function might be to seal the sensitive root dentin. The exact nature of this layer is still controversial. This layer is considered to be of dentinal origin

43. FUNCTIONS OF CEMENTUM

44. anchorage It furnish a medium for the attachment of collagen fibers that bind the tooth to alveolar bone Since collagen fibres of PDL cannot be incorporated into dentin, a connective tissue attachment to tooth is not possible without cementum

45. adaptation Cementum makes functional adaptation of teeth possible The continuous deposition of cementum is of considerable functional importance. Continuous deposition of cementum in apical area compensates for loss of tooth substance from occlusal wear. As the most superficial layer of cementum ages, a new layer of cementum must be deposited to keep the attachment apparatus intact. This process also serves to maintain the width of the periodontal ligament space at the apex of the root.

46. REPAIR Cementum serves as a major reparative tissue for root surfaces Damage to roots such as fractures and resorptions can be repaired by deposition of new cementum Cementum forms during repair resembles cellular cementum because it forms faster but it has a wider cementoid zone and the apatite crystals are smaller.

47. cEMENTO -ENAMEL JUNCTION 1) In approximately 60% of teeth cementum overlapping the cervical end of enamel for a very narrow area at the CEJ . This occurs as a result of premature degeneration or retraction of the reduced enamel epithelium at the cervical region of enamel . This allows for the adjacent mesenchymal cells to invade and intervene between enamel and its covering epithelium . The mesenchymal cells differentiate into cementoblasts and deposit cementum on enamel surface .

48. 2) 30% of all teeth, cementum meets the cervical end of enamel in a knife or edge-to-edge pattern . 3) In approximately 10% of teeth, cementum does not meet enamel where a zone of root dentin appears devoid of cementum . This can result in dental hypersensitivity as the gingiva recedes exposing the underlying root dentin 4)In some rare cases, a fourth type of cemento -enamel junction is seen.In these cases, the enamel overlaps the cementum

49. TYPES OF CEJ CEMENTUM OVERLAPS ENAMEL 60-65% BUTT JOINT 30% DO NOT MEET 5-10%

50. CEMENTO-DENTINAL JUNCTION The terminal apical area of the cementum where it joins the internal root canal dentin. The CDJ is a wide zone containing large quantities of collagen associated with GAGs resulting in incresed water content which contributes to stiffness. This reduction in mechanical property helps to redistribute occlusal loads to alveolar bone. 2 to 3 micrometer’s wide Stable with age

51. The dentin surface upon which cementum is deposited is relatively smooth in permanent teeth The cementodentinal junction in deciduous teeth, however, is sometimes scalloped

52. INCREMENTAL LINES Called lines of salter seen during the process of cementogenesis . The period of rests are associated with these lines These lines are closer in acellular cementum as this is formed slowly Whereas in cellular cementum, theses lines are widely spaced because of increased rate of formation.

53. CEMENTAL RESORPTION Local causes : Trauma from occlusion, orthodontic movement, cysts and tumors, periapical and periodontal disease. Systemic causes: Calcium deficiency, Hypothyroidism, Pagets disease . In severe cases, resorption may continue into the dentin.

54. MICROSCOPICALLY : Bay like concavities in the root surface Multinucleated Giant cells and large mononuclear macrophages found. Not continuous and is alternated by periods of repair and deposition . Newly deposited cementum demarcated from old by deeply staining irregular line- Reversal line Reversal line- Has few collagen fibrils and highly accumulated proteoglycans with mucopolysaccharides .

55. CEMENTAL REPAIR Remodelling of cementum requies the presence of viable connective tissue This can occur in vital or non vital teeth. In most cases of repair, there is a tendency to reestablish the former outline of root surface. This is called anatomic repair .

56. And if only a thin layer of cementum is deposited on a deep resorption surface, root ouline is not constructed and bay like recess remains. In such areas, sometimes the periodontal space is restored to its normal width by formation of a bony projection so that a proper functional relationship will result. The outline of alveolar bone in these cases follow that of root surface. This change is called functional repair.

57. EXPOSURE OF CEMENTUM TO ORAL ENVIRONMENT Cementum becomes exposed to the oral environment in case of gingival recession and as a result of loss of attachment in pocket formation. The cementum is sufficiently permeable to be penetrated in these cases by organic substances, inorganic ions and bacteria. Bacterial invasion of the cementum occurs frequently in periodontal disease.

58. AGE CHANGES IN CEMENTUM Cementum formation continues throughout life and is deposited at a linear rate. More cementum is deposited apically than cervically . There is a tendency for cementum to reduce root surface concavities thus thicker layers may form in root surface grooves and in furcation areas. continuous deposition

59. Abnormalities of CEMENTUM

60. HYPERCEMENTOSIS Hypercementosis is a non neoplastic deposition of excessive Cementum that is continuous with the normal radicular cementum . Factors Associated with Hypercementosis LOCAL FACTORS Abnormal occlusal trauma Adjacent inflammation Unopposed teeth [e.g., impacted, embedded, without antagonist)

61. SYSTEMIC FACTORS Neoplastic and non neoplastic conditions including benign cementoblastoma , cementifying fibroma, cemental dysplasia Acromegaly and pituitary gigantism Paget's disease of bone Rheumatic fever Thyroid goiter

62. CLINICAL FEATURES : Hypercementosis occurs predominantly in adulthood, and the frequency increases with age. Its occurrence has been reported in younger patients, and many of these cases demonstrate a familial clustering, suggesting hereditary influence. RADIOGRAPHIC FEATURE: Radiographically, affected teeth demonstrate a thickening or blunting of the root. but the exact amount of increased cementum often is difficult to ascertain . Radiolucent shadow of PDL and radiopaque lamina dura always seen NO TREATMENT REQUIRED

63. Description and Location Cemental tears or separations can occur either as a split within the cementum that follows one of its incremental lines or more commonly as a complete separation along the cemento -dentinal border. The cemental fragment can remain partially attached or be completely detached from the root surface. CEMENTAL TEARS

64. ANKYLOSIS Fusion of cementum and alveolar bone with obliterated PDL Occurs in teeth with cemental resorption After periodontal inflammation, tooth replantation, occlusal trauma. Results in resorption of root and its gradual replacement by bone. Lack physiological mobility, metallic percussion No proprioception because pressure receptors in periodontal ligament are deleted or not function correctly .

65. Radiographically: Resorption lacunae are filled with bone. Periodontal ligament space is missing. Treatment:  No predictable treatment can be suggested. Treatment modalities range from a conservative approach,such as resotorative intervention to surgical extraction of affected tooth .

66. CEMENTICLES Abnormal, calcified bodies in the periodontal ligament It has been postulated that they originate from foci of degenerating cells or epithelial rest cells Generally less than 0.5mm in diameter Types Free cementicles . Sessile or attached cementicles . Interstitial cementicles As the cementum thickens with advancing age, it may envelop these bodies.

67. If some HERS cells remain attached to forming root surface, they can produce focal deposits of enamel like structures called ENAMEL PEARLS. ENAMEL PEARLS

68. CONCRESCENCE Fusion of teeth by fusion of cementum, max. molars Traumatic injury or crowding of teeth in the area during the apposition and maturation stage of development may be the cause. Difficulty in extraction

69. INFLUENCE OF SYSTEMIC DISEASES ON CEMENTUM

70. HYPOPHOSPHATASIA Hypophosphatasia is a rare metabolic bone disease that is characterized by a deficiency of alkaline phosphatase. One of the first presenting signs of hypophosphatasia may be the premature loss of the primary teeth presumably caused by a lack of cementum on the root surfaces. The histopathologic examination of either a primary or permanent tooth that has been exfoliated from an affected patient often shows an absence or a marked reduction of cementum that covers the root's surface. TREATMENT: The treatment of hypophosphatasia is essentially symptomatic because the lack of alkaline phosphatase cannot be corrected

71. PAGETS DISEASE Paget’s disease is characterized by enhanced resorption of bone. Etiology: viral infection, inflammatory cause, autoimmune, connective tissue and vascular disorder. CLINICAL FEATURES : Middle age and both males and females are affected. Involvement of facial bone. MAXILLA- progressive enlargement, alveolar ridge widened, palate flattened, tooth become loosened. MANDIBLE: findings are similar but not as severe as maxilla.

72. RADIOGRAPHIC FINDING : Cotton wool appearance of paget’s bone GENERALISED HYPERCEMENTOSIS of the tooth seen . CHARACTERISTIC HISTOLOGIC FEATURE : Jigsaw or mosaic pattern TREATMENT: No specific treatment

73. HYPERPITUITARISM Gigantism is the childhood version of growth hormone excess and is characterized by the general symmetrical overgrowth of the body parts. Prognathic mandible, frontal bossing, dental malocclusion, and interdental spacing are the other features. Intraoral radiograph may show hypercementosis of the roots. Acromegaly is characterized by an acquired progressive somatic disfigurement, mainly involving the face and extremities, but also many other organs, that are associated with systemic manifestations. Dental radiograph may demonstrate large pulp chambers and excessive deposition of cementum on the roots

74. NEOPLASMS ASSOCIATED WITH CEMENTUM

75. CEMENTOBLASTOMA The benign cementoblastoma is probably a true neoplasm of functional cementoblasts which form a large mass of cementum or cementum-like tissue on the tooth root. Clinical features Under age of 25 years, mostly in mandible, 1 st PM Slow growing, may cause expansion of cortical plates Radiographically, well circumscribed dense radioopaque mass often surrounded by a thin ,uniform radiolucent line. Treatment : Extraction of tooth though pulp is vital as it might cause expansion of jaws

76. CEMENTIFYING FIBROMA The neoplasm is composed of fibrous tissue that contains a variable mixture of bony trabeculae, cementum like spherules or both. origin of these tumors is odontogenic or from periodontal ligament. CLINICAL FEATURE : 3 RD and4 TH decades, female predilection,mandi.PM and molar seldom cause any symptoms and are detected only on radiographic examination . Radiographically, the lesion most often is well defined and unilocular it may appear completely radiolucent, or more often varying degrees of radiopacity TREATMENT : Enucleation of the tumor

77. APPLIED ASPECTS

78. Zander and Hurzeler (1958) stated that cementum is a better age estimating tissue than others Incremental lines in cementum can be used as most reliable age marker than any other morphological or histological traits in skeleton Evaluation of annual incremental lines of dental cementum is one of potentially valuable methods for biological age estimation in forensic anthropology and digitalized visual analysis system enhances the count and provides better results. ( Bojarun et al,2003)

79. CONCLUSION

80. Clinical Periodontology and Implant dentistry- Lindhe 4th Edition Carranza’s Clinical Periodontology- 10th Edition Orban’s oral histology and embryology- 12th Edition TenCate’s Oral histology- 6th edition PERIO 2000 - Dental cementum: the dynamic tissue covering of the root. - Dieterd . Bosshard &t Knuta . Selvig REFERENCES